<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
    // [] {}
    var dataArr = [10, 20, 50, 100];
    dataArr.forEach(function (item, index) {
        // console.log(item, index);
    });


    var obj = {left: 300, top: 200, width: 500};
    for(var key in obj){
        console.log(key);
        console.log(obj[key]);
    }

</script>
</body>
</html>